This invention relates to an ultrasonic horn assembly having a connector for connecting two major stack components of the assembly together.
Ultrasonic horns are used to distribute ultrasonic energy in a variety of industrial processes. One example involves bonding of two thermoplastic sheets of material together in the manufacture of personal care products such as diapers.
Ultrasonic horn assemblies have a number of distinct components, which are connected in a stack. In one arrangement these components may include a power excitation device known as a converter (or driver assembly), amplitude modification devices known as boosters, and an ultrasonically energized tool known as a horn, which contacts a workpiece. These components have been connected to each other, for example, by use of a fully threaded, high strength steel stud. A drawback of this arrangement is that a high-pressure center contact area tends to form in the area immediately around the stud at the interface between the two stack components being connected. In particular, clamping forces are concentrated in an area immediately around the stud. The clamping pressure at the interface holding these two components together is significantly greater immediately around the stud than it is at the periphery of the mating surfaces remote from the stud. As such, the clamping force that holds the components together degrades peripherally away from the stud. As ultrasonic energy is transmitted across this interface over time during extended operation of the horn assembly, the variation in clamping force at the interface facilitates various wear phenomena such as fretting, as well as burning or oxide buildup, as the components are imperfectly joined. The variation itself degrades the efficiency of energy transfer, and the resulting wear and oxide build up further degrade this efficiency. To address this wear it is necessary to periodically disassemble the horn assembly and refinish the stack components at the interface therebetween.